1. Field of the Invention
This invention relates to zoom lens mountings, and more particularly to a driving torque transmitting mechanism for the variator lens cell in the zoom lens mounting having a single actuator member for focusing and zooming.
2. Description of the Prior Art
The mechanical mountings for zoom lenses of which the focusing and zooming are performed by only one actuator member are known, for example, in U.S. Pat. No. 4,448,496 (Japanese Laid-Open Patent Application No. SHO 56-54408). The mechanical mounting disclosed in the above-identified patent is adapted to be used with the 4-component zoom lens including a focusing lens component, a variator, a compensator and a relay lens.
In this type of mounting, when to perform zooming, the single actuator member is axially moved. The mechanism for transmitting the driving power from the actuator member to differential axial movement of the variator and compensator has been constructed in such a way that the cam followers radially extending outwardly of their lens cells fitted in the body tube take their places at the cross points of the camming slots provided through the wall of the body tube with the camming grooves or slots formed in the inner surface of an axially slidable sleeve fitted on the outer diameter of the body tube and arranged to move as a unit with the actuator ring when zooming. As the slope of each of the camming slots of the body tube and the outer sleeve varies with the focal length of the entire system, therefore, when the angle the two slopes of the paired camming slots make becomes smaller, the required value of the driving power for axially moving each of the lens cells rapidly increases with increase in the stress to the operating mechanism. If the lens cells are forced to move, they are inclined with the optical axis, so that the imaging performance is worsened.